Implications of Parasites Lacking Plasmodium falciparum Histidine-Rich Protein 2 on Malaria Morbidity and Control When Rapid Diagnostic Tests Are Used for Diagnosis.

Background: Rapid diagnostic tests (RDTs) are an important tool for malaria diagnosis, with most using antibodies against Plasmodium falciparum histidine-rich protein 2 (PfHRP2). Reports of P. falciparum lacking this protein are increasing, creating a problem for diagnosis of falciparum malaria in locations without quality-assured microscopy.
Methods: An agent-based stochastic simulation model of P. falciparum transmission was used to investigate the selective pressure exerted on parasite populations by use of RDTs for diagnosis of symptomatic cases. The model considered parasites with normal, reduced, or no PfHRP2, and diagnosis using PfHRP2-only or combination RDTs.
Results: Use of PfHRP2-only RDTs in communities where a PfHRP2-negative parasite was introduced during the simulation resulted in transmission of the parasite in >80% of cases, compared with <30% for normal or PfHRP2-reduced parasites. Using PfHRP2-only RDTs in the presence of PfHRP2-negative parasites caused an increase in prevalence, reduced RDT positivity within symptomatic patients but no change in the number of antimalarial treatments due to false-negative RDT results. Diagnosis with PfHRP2/Pf-Plasmodium lactate dehydrogenase combination RDTs did not select for PfHRP2-negative parasites. Conclusions: The use of PfHRP2-only RDTs is sufficient to select P. falciparum parasites lacking this protein, thus posing a significant public health problem, which could be moderated by using PfHRP2/Pf-Plasmodium lactate dehydrogenase combination RDTs.